The ISL space frame, shown in Figure 9, also supports the SVX II and all associated readout and utility components. (Layer 00 is supported by the beam pipe.) The central barrel of the ISL consists of silicon ladders that are staggered alternately at either 22.6 or 23.1 cm in radius from the nominal beam line. This layer is extended by an additional set of ladders mounted at 19.7 or 20.2 cm in radius that are contained in the barrels at each end of the space frame.
The outermost layer of the ISL is populated only in these end barrels, and consists of ladders mounted alternately at radii of either 28.6 or 29.0 cm. Temperature control is provided for the ISL electronics by a water/ethylene glycol coolant mixture flowing in aluminum tubes attached to beryllium ledges mounted on the space frame.
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The six layers of ladders that comprise the SVX II and Layer 00 portion of the
tracker are arranged in twelve azimuthal wedges that alternate in
radius within each layer. The SVX II sensors are arranged
in three barrels, each four sensors in length. Water/glycol coolant for the
silicon and electronics flows within internal channels that are machined into
the beryllium bulkheads at each barrel end. The expected silicon temperature
in the SVX II ranges between 10 and 15 
C[17].
Layer 00 cooling is still under study, with the goal to keep silicon
temperatures below approximately 5 
C in order to improve radiation
resistance.
All components of the CDF II silicon system use port cards to receive data from and transfer control signals to the SVX3D readout chips. These port cards also regulate power to the hybrids and carry components that translate the SVX3D output signals into optical format for transmission outside the tracking volume. They are mounted at the locations indicated in Figure 3. Since the port cards account for 35% of the total silicon system heat load of approximately 4 kW, they also receive active cooling.